Timmer Aurora Intercept

[D. Hayes]

Tornado yap aside and vehicle design in mind--

He should have made a window clip to connect the two windows together. That way when the glass went up the lexan would go up and lock into place. Man I wish I had the resources to build my own interceptor.

 

[Chuck Hurley]

This thread makes me think about something that Dr. Wurman said about not being able to accurately see the bottom 50 feet of a tornado. Dustin and Jeff alluded to this fact because the storm damage are not accurate due to some dirt clods have been moved around. So if they are just using radar then at what height is the EF determination made for a tornado that is in a field.

Hopefully what I'm trying to say is apparent because you guys are much more experienced at this type of analysis then I am. I'm just a newbie learning as much as I can.

Thanks,

Chuck

 

[Jeff Duda]

Chuck, you should re-read Jeff's post. EF scale rating is determined by damage done (at the surface, presumably), not by measured wind speeds in the tornado. As Jeff mentioned, if a tornado packing 130 mph winds moved through an empty field and hit no EF-scale damage indicators, then it would be forced to be rated EF0, even though the winds associated with it may have been higher. The EF-scale is a DAMAGE scale, not a wind speed scale. The wind speeds were just matched to the damage with the idea that it took those kinds of winds to do that kind of damage.

Regarding later posts (after Jeff's) it would be rather difficult to pinpoint the area of the circulation some damage indicators are in because a lot of tornadoes (including ones like the Goshen Co., WY and the Aurora tornado) are multi-vortex, so the damage pattern is much more complex. You can clearly see the multiple vortices in the TVN video.

 

[Darren Addy]

IMO an accurate measurement should be considered over human estimates when it comes to wind speeds...but that just raises more questions and debate so I just go along with the system that is currently setup and in place by people a whole lot smarter than me

I'd agree with this and just mention that accurate measurement begins with knowing the accuracy of your annemometer. I have no idea what brand/model is used on the Timmermobile, but they are generally designed for highest accuracy in the wind speeds that we will experience most (not inside a tornado or hurricane).

Check out the respected inspeed chart for instance:
http://www.inspeed.com/images/large/cal-chart.gif

It is "right on" at about 25 mph and already reading 2 mph off at 45 mph. Assuming a linear divergence, that anemometer would be reading 10 mph high (telling you 135) at an actual 125 mph wind speed.

I'm guessing that the more you spend for an anemometer the more science-grade instruments you get (as in... Vortex 2 doesn't use inspeeds) but my point is that you can't assume your instrument is necessarily accurate at those higher speeds either.

 

[Chuck Hurley]

Chuck, you should re-read Jeff's post. EF scale rating is determined by damage done (at the surface, presumably), not by measured wind speeds in the tornado. As Jeff mentioned, if a tornado packing 130 mph winds moved through an empty field and hit no EF-scale damage indicators, then it would be forced to be rated EF0, even though the winds associated with it may have been higher. The EF-scale is a DAMAGE scale, not a wind speed scale. The wind speeds were just matched to the damage with the idea that it took those kinds of winds to do that kind of damage.

Regarding later posts (after Jeff's) it would be rather difficult to pinpoint the area of the circulation some damage indicators are in because a lot of tornadoes (including ones like the Goshen Co., WY and the Aurora tornado) are multi-vortex, so the damage pattern is much more complex. You can clearly see the multiple vortices in the TVN video.

That's the point I was trying to say sorry about the confusion. So tornado reporting data would be skewed because of the tornado's that do churn up some dirt but don't do any damage. Also you had answered some background questions that I had too with your post. Appreciate the education.

Chuck

 

[Jared Farrer]

It was a very powerful tornado in a multi-vortex phase and rapidly strenghting when they intercepted it. I wouldnt be surprised to hear that the wind speed is pretty close to being correct. Being they were in the core flow and the tornado was rapidly intensifying, i.e. suction vortices. Ears popping, and you could hear in the video the sound of whooshing that pressure was causing some serious issues. Alot of interesting stuff going on in that video. It seemed with the pressure drop and the wind that air forced itself violently into the vehical imploding the window!

Id be interested at the pressure drop they experienced but I dont think they had any pressure measuring devices on board at the time.

P.S. Of course very accurate wind speeds are hard to obtain. So their is almost always a degree of error it cant be helped in most forms of measuring. But round about 135 +/- 10 or so is still a good estimate. And it would seem to me to be very plausible!

 

[Rob Wadsworth]

I wonder...how much wind speed does it require to get a vehicle to start tumbling?
Or how much wind speed just to knock it over...or for that matter - just to push it a few feet?

135mph wind speed? Hmmm...what should happen at that speed? If it is enough to tear up a house, it should be making a car tumble at least a few times...

 

[Olivier Staiger]

> I wonder...how much wind speed does it require to get a vehicle to start tumbling?


depends on the car.. size.. weight ... cx... aerodynamics .. position ...

I guess there's a huge difference if you are in a Ford F350 heavy duty truck or in a smart car ...

the best chase car would probably be a DMC DeLorean , provided it comes with that special upgrade optional button.. to drive back to the future ... ;-)

 

[Paul Austin]

The SRV intercept occurred not too long after the circulation's development, as it made its southward road crossing during this early stage of the tornado's life cycle. That said, the SRV was the only substantial structure to be impacted, so no one can be certain of the actual wind speeds during the point of impact. I believe some center-point irrigation units were damaged/twisted shortly after, but someone else would have to confirm that. I would personally wonder about the slipstream effects and high velocity error magnification if only to err on the side caution. But I'm by no means a skeptic. I believe a wind gust within the developing circulation even at this early stage is completely within the realm of possibility. Wind speed development within a tornado can certainly be (and realistically always is) a non-linear process. The tornado certainly appeared to attain maximum strength near the time of the house impact, and while I agree that this assessment is probably somewhat accurate, without additional structure along its path, it is no more than an educated guess. The damage assessment and resulting EF scale assignment and path representation was based purely on the damage inflicted on the structures impacted. Most of the Aurora tornado's track was across open field. I certainly wouldn't call myself a firm "believer" in the 138mph measurement just yet; just keeping an open mind

 

[cdcollura]

Good day all,

I saw this stuff on the 17th (June) ... Sitting hopelessly in Miami, Florida at work with my boss out on a cruise and me unable to chase that week (the ONLY week I could not chase - Go figure).

Awesome stuff and great job (hat's off to Timmer and his crew) and glad they got out of there with (only) a scratch.

Video like that, with measurements, is crucial scientific footage as well.

The closest thing to that with myself was last year (2008) in Kearney, NE on the 29 of May (130+ MPH).

I bet the TIV crew was drooling (worse than me at work) after seeing that ;-(

 

[Paul Austin]

I do have to admit, though the situation and resulting damage and injury was anything but funny, I have a hard time not finding Reed's comments immediately prior to the point of impact a bit amusing: "Maybe I should shut the window. What do you think?"

What do you think???!! Um...yeah, now would be a good time to do that, I think. I don't know, should we form a committee? No wait, I heard somewhere you're supposed to open windows to relieve pressure, so the house doesn't explode, right?

Sorry, Reed. You just made it too easy

 

[Paul Austin]

Good day all,

I saw this stuff on the 17th (June) ... Sitting hopelessly in Miami, Florida at work with my boss out on a cruise and me unable to chase that week (the ONLY week I could not chase - Go figure).

I feel your pain. Though I was able to make it back out for this spectacular event after a less than spectacular two weeks in May, I enjoyed last year's May 22-25 tornado fest from the comfort of my office, while Marc and Sarah (family and team members) made numerous intercepts in KS and OK. The chips fall unkindly sometimes.

 

[Jason Foster]

Reed said the truck wasn't suppose to intercept tornadoes.

A few things I think not mentioned about the Timmermobile and maybe a clarification I need.

My observations have shown that Reed's vehicle is just a simple outer shell, and possibly may even be removable from the Tahoe based truck. This is why there are two windows; an outer and inner, which the inner is just the factory glass. But I am unsure about the construction of the vehicle. Personally, I find it surprising it be so hard to weld such a vehicle together with more usability and safety than both the TIV and Reed's little red wagon.

I also seem to remember that Reed said the vehicle was never intended to intercept a tornado directly, only get really close? So I don't know if this was an intentional intercept or a mistake on his (or whomever was driving) part.

 

[jeremy wilson]

I wonder...how much wind speed does it require to get a vehicle to start tumbling?
Or how much wind speed just to knock it over...or for that matter - just to push it a few feet?

135mph wind speed? Hmmm...what should happen at that speed? If it is enough to tear up a house, it should be making a car tumble at least a few times...

Just wait, we'll all find out very soon when one of us yahoos get rolled. And yes I'm including myself in the yahoo department.

 

[Skip Talbot]

I wonder...how much wind speed does it require to get a vehicle to start tumbling?
Or how much wind speed just to knock it over...or for that matter - just to push it a few feet?

135mph wind speed? Hmmm...what should happen at that speed? If it is enough to tear up a house, it should be making a car tumble at least a few times...

One of the biggest factors is what direction the car is facing relative to the wind. A car can easily withstand 130 mph of horizontal wind when its facing into it. From the side, however, the car is going to start rolling. There is also a vertical component in the wind, however, and even if the car is facing perfectly into the wind, this will lift the car up and it will then roll end over end.

Tornados are extremely complex structures with suction voritcies and sub vorticies inside of those. The wind speed varies greatly over a matter of feet. Even, if you could get your vehicle to track the direction of the outer circulation, keeping up with the sub vorticies would be impossible. An airfoil that generates negative lift might help substantially, however. Maybe even if it could pivot freely so that it tracks with the smaller vorticies. I remember one of the tornadoes that tracked through the Chicago area here hit a small airport, and the canard aircraft that are parked nose down generate negative lift in that position and remained in their spots. The more conventional aircraft like the Cessnas, however, were thrown about and destroyed.